The invention relates to a hydraulic fluid delivery or circulation device, such as a pump, that is structurally and thermodynamically efficient, and a method for installing the same.
The invention relates to a hydraulic fluid delivery or circulation device (such as a pump) with a displacement unit mounted in a housing and set in rotation through a drivable shaft unit and which comprises a rotor mounted rotationally secured on the shaft in a pump chamber, and with means which during rotation of the rotor produce at least a first region (suction region) with increasing volume and at least a second region (pressure region) with reducing volume, wherein the first region is connected to a suction connection of the delivery device and the second region is connected to a pressure connection of the delivery device.
Hydraulic delivery devices of the above kind are known. These are formed for example as vane pumps, locked vane pumps, rotary piston pumps or the like. It is known to use delivery devices of this kind in power steering devices, auxiliary braking devices or the like in motor vehicles wherein hydraulic oil is pumped out of a tank to a hydraulic consumer with an attendant increase in pressure.
It is likewise known for the pump chamber to be defined by surfaces which are aligned radially relative to the shaft and abut the rotor in pressure-tight manner, and for the pump to have communicating ducts to the at least first and second regions and to have a flow regulator arrangement for regulating the volume flow of the delivery device.
It is also known to drive the delivery device through an internal combustion engine of the motor vehicle wherein a speed of the rotor of the delivery device is changed in accordance with the rotational speed of the combustion engine of the vehicle. The delivery device then produces a volume flow which fluctuates in dependence on the speed of the internal combustion engine and thus the speed of the delivery device. In order to establish a substantially constant maximum volumetric flow at a consumer, flow regulator arrangements are known which are integrated in the delivery device and by means of which a booster connection from a pressure region to a suction region of the delivery device can be released. A number of guide paths (ducts) are hereby established inside a housing of the delivery device which have to be coupled in sealed manner to the pressure or suction regions of the displacement unit.
It is further known to journal the shaft of the delivery device in bearing regions of the housing. As a result of the pressure-tight guidance of the rotor inside the pump chamber it is necessary to provide a bearing for the shaft with the smallest possible bearing clearance and at the same time to mount the shaft pressure-tight using the fewest possible individual parts.
Furthermore the invention relates to a hydraulic delivery device having a displacement unit mounted in a first part of a housing and comprising a rotor which can be set in rotation through a drivable shaft, and with a cover for closing the first housing part as well as with a holder for the delivery device connected to the cover.
The first housing part can be closed by a cover on which a holder for the delivery device is screwed. As a result of this type of connection the cover which in known delivery devices is made from aluminum and is usually made by the pressure die casting method, is relatively large so that a correspondingly large installation space has to be prepared for the delivery device. This is disadvantageous particularly when using the delivery device in connection with a vehicle since here the delivery device is accommodated for example in the engine compartment in which the space available for the delivery device is only very small.
The invention further relates to a hydraulic delivery device with at least one displacement unit mounted in a housing wherein the displacement unit is connected to a suction connection and to a pressure connection of the delivery device, and the suction connection is connectable to a source, more particularly a tank, supply container, reservoir or the like of a medium to be delivered, through a pipe fitting which can be connected pressure-tight to the suction connection.
Furthermore the invention relates to a method for assembling a delivery device wherein a pipe fitting which engages on a housing of the delivery device and is connected pressure-tight to a suction connection can be positioned for connecting with a pipeline leading to a source of the medium which is to be delivered.
The displacement unit mounted in the housing sucks in the oil through a connecting pipe, by way of example a flexible pressure hose, and delivers this through an increase in pressure to the power steering. A connection between the suction connection of the delivery device and the connecting pipe is produced through a pipe union onto which the connecting pipe can be pushed. It is already known to make the pipe union of plastics. A connection between the pipe union and the housing of the delivery device is made so that the pipe union engages in a blind opening wherein an external circumference of the pipe union corresponds substantially to an inner circumference of the blind opening, and the blind opening has at least one radially inwardly pointing projection which engages in a corresponding recess of the pipe union. Axial fixing of the pipe union is hereby achieved. In addition a sealing device is provided between the housing and pipe union to allow a pressure-tight connection.
Through a snap-fitting or detent connection between the pipe union and the housing of the hydraulic delivery device the pipe union can be turned in the blind opening after the hydraulic delivery device has been fitted, for example in the engine chamber of a motor vehicle. It is hereby possible to align the pipe union in order to find the best possible position for connecting the connecting pipe to a tank which contains a medium which is to be delivered. With the known hydraulic delivery device it is a disadvantage if the pipe union can turn inside the blind hole once fitting has taken place. This can lead for example through the appearance of vibrations during use of the hydraulic delivery device to a distortion of the pipe union so that a connection between the pipe union and connecting pipe to the tank can leak or even come undone in an extreme case.
The invention further relates to a hydraulic delivery device having a displacement unit which delivers a medium from a suction connection standing under the output pressure to a pressure connection connectable with a consumer and standing under the consumer pressure, and a regulating device for adjusting or restricting a volume flow conveyed by the delivery device. In the sense of the invention output pressure is to mean suction intake pressure, input pressure or the like which as a rule is smaller than or equal to atmospheric pressure.
Delivery devices of this kind are normally driven by the internal combustion engine so that with a fluctuating speed of an output shaft of the combustion engine the pump speed is likewise subject to fluctuation. Through the fluctuating pump speed a variable volume flow is set by means of the hydraulic delivery device and likewise rises as the pump speed increases. A consumer connected to the pump requires per se only a certain maximum volume flow so that too much volume flow is set by the pump at high speeds. It is known here to provide the pump with a flow regulating valve which regulates a volume flow to a consumer by releasing an outflow channel from a pressure side to a suction side of the pump.
It is known to equip flow regulating valves of this kind with an additional throttle function. To this end a valve piston of the flow control valve has an axial projection which can be passed through a fixed orifice. The free through-flow cross-sectional area of the orifice is adjusted according to the position of the valve piston. This produces an additional throttling of the volume flow which is dependent on the flow regulating piston. The drawback here is that the throttle function is linked to the function of the flow regulating valve so that this likewise throttles dependent on the path of the flow regulating valve. Furthermore a throttle function of this kind is dependent on the pressure in the pressure collecting chamber of the delivery device (operating pressure) since the flow regulating valve is regulated by a difference in pressure between the pressure in the pressure collecting chamber of the delivery device and the consumer pressure. Furthermore there is the drawback that through the combination of the flow regulating valve with the throttle a relatively expensive assembly is required which has to be carried out with great care in order to be able to set exact volume flow characteristics. The flow regulation and throttling must be matched precisely with each other in order to be able to set a desired volume flow characteristic of the hydraulic delivery device.
The object of the invention is therefore to provide a hydraulic delivery device which compared with the prior art requires less structural space, is simple to construct, requires fewer component parts and furthermore helps in reducing the fuel consumption of the vehicle fitted with same.
According to the invention this is achieved by means of a hydraulic delivery device in that the pump chamber is defined on its one side by a plate which produces a hydraulic control function of the hydraulic delivery device, a sealing device for sealing regions of the delivery device which are under different pressures and an axial positioning of the shaft after fitting and centering the plate. Thus advantageously with a single component part a seal is possible between the different functional regions of the delivery device wherein at the same time a precision bearing of the shaft and its sealing is produced substantially free of axial clearance. Through the plate provided according to the invention (hereinafter called the control plate) a compact construction of the delivery device is achieved which consists of few individual parts, is easy to fit and can thus be manufactured cost-effectively.
In a preferred embodiment of the invention it is proposed that the control plate has a through hole through which the shaft is guided, and the through hole preferably has design features which correspond with those of the shaft to form an axial stop for the shaft. It is hereby readily possible to form a defined stop for the shaft which allows an exact axial alignment of the shaft. This is thus secured against axial displacement and can more or less not fall out of the opening provided in the housing of the delivery device for receiving the shaft. Furthermore additional component parts such as spring rings or tapered discs are unnecessary which reduces the weight and costs.
In a further preferred embodiment of the invention it is proposed that the plate has a radially aligned surface which bears flat against a likewise radially aligned surface of the housing and hereby undertakes the sealing function between different channels or bores opening into the surface of the housing in which different functional elements, more particularly flow control valve, pressure relief valve and main flow throttle, are arranged, as well as seals openings standing under different pressures. An optimum seal can thus be readily produced between the individual regions of the delivery device, particularly when the surface of the plate is pressed under hydraulic pressure against the surface of the housing. The plate is hereby biased indirectly with the hydraulic pressure through a pressure plate.
In a further preferred embodiment of the invention it is proposed that the plate has apertures or recesses forming suction kidneys or pressure kidneys respectively, more particularly also a control pressure bore provided in a pressure cell for a main flow throttle piston adjoined by the highest pressure produced in the delivery device, whereby the other recesses undertake the connection of the displacement unit to the suction or pressure channels or regions of the delivery device. Several control functions of the hydraulic delivery device can hereby be easily achieved by means of the plate through a defined configuration of the recesses and openings.
A further preferred design of the invention is produced in that the full-length opening has an approximately elliptical cross-section wherein a rotary axis of the shaft coincides with a center point of a semi-circular shaped area of the full-length opening after fitting and centering the plate, and a bead positioned coaxial to the rotary axis forms a ring step for receiving the guide section.
An embodiment is likewise preferred wherein the surface of the plate seals the suction kidneys and the pressure kidneys of the delivery device from each other.
According to the invention the plate is pressed on the valve side indirectly (through a pressure plate on the cover side and a spacer ring) hydraulically against the housing part through an operating pressure of the delivery device, whereby the plate has a ring groove through which the under vane areas on the rotor are biased with pressurized medium.
Furthermore it is an object of the invention to provide a hydraulic delivery device which has a simple compact construction as well as is simple to fit, has larger pressure chambers and/or smaller external dimensions and where applicable has reductions in weight.
This is achieved by a hydraulic delivery device wherein the cover and the holder are in one piece or connected together secured against rotation through a screw and a projection engaging in an opening. By omitting the screw connection it is possible to provide a compact structure so that a delivery device can be achieved which only requires a small installation space whilst its weight is reduced. Furthermore this eliminates the costs of fitting the holder and those for the screw connection which is required with the known delivery device to fix the holder on the cover.
In an advantageous embodiment of the delivery device the cover and/or the holder are produced by the deep drawing method. Through the thin-walled cover the structural space saved is used to enlarge the pressure chamber of the delivery device and/or to design it with better flow properties whereby the load absorption can be reduced. The cover and/or the holder are made in one or more moves from a sheet metal which consists for example of steel, aluminum or an aluminum alloy. The manufacture of the cover and/or the holder through deep drawing is possible and cost-effective since additional processing is no longer necessary.
Thus compared to the pressure die cast aluminum covers, structural space is saved here which produces flow favorable pressure chambers and thus better degrees of efficiency. Furthermore the thinner-walled steel cover is lighter than a thick-walled cast aluminum cover despite the higher specific material weight.
A further advantageous embodiment is produced in that the cover is formed pot-shaped and produces a closed pressure collecting chamber with the first housing part.
According to the invention in the fitted state the cover applies axial contact pressure on the displacement unit through at least a first seal.
According to a further embodiment the pressure collecting chamber is sealed from the atmosphere through at least a second seal which in the fitted state of the cover is pressed against the first housing part.
The invention is further concerned with the task of producing a hydraulic delivery device of the generic type and providing a method for fitting the delivery device wherein a secure connection remains guaranteed between the pipe union and a connecting pipe on one side and the pipe union and the housing of the delivery device on the other side.
According to the invention this is achieved through a hydraulic delivery device wherein the pipe union can be fixed radially and axially in the blind opening by means of external fastening. Thus a relative movement between the pipe union and the housing can be avoided so that the pipe union retains its desired position. A mechanical strain on the connecting points between the pipe union and connecting pipe is hereby avoided so that the pipe union cannot cant relative to the connecting pipe. It is hereby possible at any time, even with mechanical strain for example through vibrations, to guarantee the tightness and reliability of the connecting point between the pipe union and the connecting pipe.
In a preferred embodiment of the invention it. is proposed that the fixing means is a self-tapping screw whose thread circumference partially cuts a wall of the pipe union. After positioning the pipe union the screw can hereby be tightened by means of a tool whereby the self-tapping thread engages in areas in the sleeve of the pipe union and thus displaces the material of the pipe union in part. A simple but secure axial and radial fixing of the pipe union is hereby achieved.
Particularly when a bore holding the fixing screw runs perpendicular to the blind opening receiving the pipe union, maximum holding force can be applied to fix the pipe union axially and radially.
In another preferred embodiment of the invention it is proposed that the fixing means are formed by at least one displaced material area of the housing section enclosing the pipe union. After positioning the pipe unit the material of the housing can hereby be displaced by suitable tools in defined manner so that this material is forced into a recess preferably provided on the pipe union so that axial and radial securement of the pipe union is produced at the same time.
It is particularly preferred if as pipe union a plastics pipe union is used which consists of a polyimide or a polyamide with a proportion of glass fibers which preferably amounts to between 30 and 60% in the case of polyamide and 10% in the case of polyimide. The pipe union which is made of this plastics is hereby on the one hand relatively temperature-resistant and on the other in particular has the required strength to allow the material of the housing of the delivery device which normally consists of pressure cast aluminum to displace into a corresponding recess without damaging the pipe union. Many other plastics are unsuitable for such flanging processes.
Furthermore this is achieved through a method with the said features in that after fitting the delivery device and connecting the pipe union to a connecting pipe leading to a tank, the pipe union is fixed. It is advantageously possible during fitting to retain a certain flexibility through the ability of the pipe union to rotate on the housing so that a connection between the pipe union and the connecting pipe can be produced in optimum manner. Only after this connection has been made is the pipe union fixed so that a subsequent loosening or release of the pipe union, and thus of the connecting point between the pipe union and connecting pipe, which may arise particularly during use of the hydraulic delivery device, is ruled out. The pipe union is preferably fixed by displacing either the material of the pipe union and/or the material of the housing in part so that at least a rear cut section is formed between the pipe union and the housing.
A further preferred embodiment of the invention is produced in that the bore runs at an angle of 90 degrees to an axis of rotation of the pipe union.
A center axis of the bore thereby preferably runs outside of the blind opening.
In a preferred embodiment a collar of the pipe union engages in a ring groove of the housing, and a bead of the housing engaging round the ring groove is deformable at least in part over the collar.
According to the invention the collar has over its circumference several recesses, in particular symmetrically spread out, into each of which a section of the bead can be deformed.
The recesses are preferably formed like segments of a circle.
The invention is further concerned with providing a hydraulic delivery device of the generic type wherein different volume flow characteristics can be readily achieved in dependence on a speed of a rotor of the delivery device and independent of the position of the flow regulator piston. Furthermore no additional build up of pressure is to be produced to operate a throttle piston.
According to the invention this is achieved through a hydraulic delivery device in that a pressure collecting chamber of the delivery device is connected to the pressure connection of the delivery device through a variable throttle device which operates independently of an operating pressure in the pressure collecting chamber of the delivery device. A volume flow regulation can thereby be produced which is substantially independent of the pressure prevailing in the pressure collecting chamber (work pressure).
Particularly if as is preferred the throttle device is a valve assembly which influences in dependence on a differential pressure between the consumer pressure of the delivery device and a pressure inside a cell in front of a pressure kidney of the displacement unit a free passage cross-section of a connection between the pressure collecting chamber of the delivery device and the pressure connection of the delivery device connected to the consumer, the adjusting differential pressure, which is determined in particular by the speed of the pump, can be used to regulate the volume flow of the delivery device. Thus a regulation is possible which is substantially independent of the pressure in the pressure collecting chamber since to regulate the valve assembly substantially the differential pressure between the consumer pressure and the pressure built up in a cell inside the pump in front of a pressure kidney is used. This differential pressure is used more or less for influencing the volume flow of the consumer so that a reduction in the volume flow (consumer flow) adjoining the pressure connection of the delivery device is possible and an influence, more particularly a reduction, of the characteristic line is possible. This pressure inside the cell is more or less the maximum pressure which arises in the actual pump so that the degree of efficiency is better than when using other pressures for regulating purposes.
In a preferred embodiment of the invention it is proposed that the valve assembly has a valve piston mounted axially displaceable in a bore. The valve piston can be biased on the one side with the pressure prevailing in a cell prior to the oil outlet through a pressure kidney of the delivery device, and on the other side with the consumer pressure and the force of a spring element wherein a control device of the valve piston varies the free through-flow cross-sectional area to the pressure connection of the delivery device in dependence on the differential pressure. Valve devices known per se from flow regulating valves can hereby be applied to the design of a variable main flow throttle which is substantially independent of the operating pressure of the delivery device. Particularly when the valve piston has a regulating pin which engages through an opening of a fixed orifice, and an outer contour of the regulating pin has an axially changing contour in the area of movement of the orifice, it is possible through a simple displacement of the valve piston as a result of the differential pressure between the pressure in the pressure kidney and the consumer pressure in the pressure collecting chamber of the delivery device to change the through-flow cross-sectional area of the orifice. A contour of the regulating pin which tapers conically for example and/or widens out conically varies the free through-flow cross-sectional area. Since the position of the valve piston and thus of the regulating pin to the fixed orifice is dependent on the pressure prevailing in the cell in front of the pressure kidney, this in turn being dependent on the speed of the delivery device, different characteristics independent of the operating pressure can be readily set in dependence on the speed of the delivery device.
A further preferred design is produced where the orifice is formed in a sleeve which is pressed into the bore.
According to the invention the regulating pin is supported on a spring plate on which the spring element engages which on the other side is supported on a base of the bore.
In a preferred embodiment the spring element is supported on the valve piston on one side and on the orifice sleeve on the other.